Ion implantation devices are used in semiconductor manufacturing to introduce dopants into semiconductor wafers. Generally, an ion implantation device includes an ion source that generates charged dopant particles and an extraction electrode that extracts the particles from the ion source and initiates an ion beam along a beam path toward a target (e.g., a semiconductor wafer). Downstream of the extraction electrode, the ion beam passes through a mass analyzing chamber, which selectively separates components from the ion beam so that only ions of the desired mass are directed toward the target. The mass analyzing chamber typically is fluidly connected to a vacuum pump for establishing a sub-atmospheric pressure inside the chamber. From the mass analyzing chamber, the ion beam passes through an accelerator for accelerating the ions into a target chamber, wherein the ions are implanted into the target.
Ion implantation devices are complex and expensive to operate and maintain. A particular problem in the use of ion implantation devices is that impurities generated during the doping process accumulate on the internal surfaces of the device, and especially the internal surfaces of the mass analyzing chamber. Consequently, the internal surfaces of the ion implantation device, typically made of metallic materials, such as stainless steel or aluminum, must be cleaned on a regular basis to ensure that the device operates within specified parameters. Typically, the internal surfaces are manually cleaned with hydrogen peroxide or other suitable solvents. However, the process of manually cleaning the internal surfaces of the device is time consuming and difficult due to the small spaces within the device and lack of access to the surfaces requiring such cleaning.
When re-starting the ion implantation device following the cleaning process, the vacuum pump is activated to re-establish a sub-atmospheric pressure in the mass analyzing chamber, which in turn can cause excessive outgassing of residual solvent in the chamber. Removal of the gaseous solvent from the chamber requires additional pump-down time before the device can be put back on line. Thus, it would be desirable to minimize or eliminate the use of solvents, such as hydrogen peroxide, in ion implantation devices to reduce downtime and increase the production yield in the manufacture of semiconductor devices.
Another problem area with conventional mass analyzing chambers is that the metallic inner surfaces of the chamber are subject to wear by the high-energy ion beam that passes through the chamber. Metallic material eroded or sputtered from the inner surfaces of the chamber is transported to and implanted into the semiconductor wafer. As a result of this contamination, the semiconductor wafer will have degraded performance, reliability and functionality.
Accordingly, a continuing need exists for improvements in ion implantation systems used for the fabrication of semiconductor devices.